[1] Embarking with his unit for the Pacific area in April 1942, he saw combat in the Guadalcanal, New Guinea, New Britain and Peleliu campaigns.

He also earned the Bronze Star medal with Combat "V" for meritorious service as Artillery Observer of the 1st Battalion, 11th Marines, in action on Cape Gloucester, New Britain.

[1] He returned to the United States in November 1944, and the following month was assigned to Marine Corps Schools, Quantico, where he completed the Instructors' Orientation Course and later served as Officer in Charge of the Course and Academic Inspector until April 1948.

[1] Following this assignment, he departed the United States in June 1948 for Tsingtao, China, where he served as Assistant Chief of Staff, G-1, and Public Information Officer of Fleet Marine Force, Western Pacific, until March 1949.

On 9 April 1966 while serving as G-3, III Marine Amphibious Force (III MAF) during the Buddhist Uprising in Da Nang he met with Colonel Dam Quang Yeu, commander of the Quảng Nam Special Sector, who supported the Buddhist Struggle Movement and was attempting to lead a convoy north from Hội An into the city.

He warned Yeu that if the latter's troops continued their advance or shelled Danang Air Base, the Americans would consider it an attack upon themselves and would react accordingly.

Thirty minutes after Chaisson left to report back to Walt, Yeu ordered his artillery unit to return to Hội An, but he and the ARVN infantry stayed where they were.

[2]: 83 On 18 May Walt tasked him with securing the Hàn River bridge in Da Nang which was being contested between Struggle Movement forces and South Vietnamese Marines.

[2]: 307  He formed a close relationship with MACV commander General William Westmoreland and became his informal advisor on all Marine matters with a reputation for outspokenness.

"[3] In a press conference on 3 February 1968, he admitted that the Viet Cong had surprised the MACV command with the intensity and coordination of the Tet Offensive.

[1] Detached in June 1968, he returned to Headquarters Marine Corps where he was assigned duty as Special Assistant to the Deputy Chief of Staff (Plans and Programs).